1. Field of the Invention
This invention relates generally to abrasive materials, and is more particularly concerned with a method for making a patterned abrasive materials wherein a plurality of abrasive particles is temporarily held by an adhesive, and is subsequently fixed by a matrix material.
2. Discussion of the Prior Art
Much effort has been expended in attempting to place diamonds or other hard abrasive particles on a surface in a predetermined pattern. The pattern is desirable in that the hard particles are distributed substantially uniformly throughout a surface, or in that specific shapes containing generally uniformly distributed particles are distributed throughout a surface. By having the particles in specific shapes that are distributed across a surface, the stock removal rate, and the quality of the machined surface, can be optimized; and, more importantly, spaces between the abrasive areas allow for the removal of debris and the inflow of coolant.
Most of the prior art techniques for providing patterns of abrasive particles include the provision of metal spots onto which diamonds are electrodeposited, the diamonds then being held in place by electroplating, or by a polymeric resin or the like. Diamonds have also been hand placed to achieve a pattern. Hand setting is of course very time consuming; and, the particles have then been held in place by electrodeposition of metal to hold the particles. Holding the particles by electrodeposited metal is not fully satisfactory because insufficient metal can be provided to truly hold the particles and to resist wear; thus, the particles tend to come loose before the abrasive material has been used enough to wear the particles. Once one stone, or particle, is loosened, there is less support for adjacent particles, and one is likely to lose a number of additional particles very quickly. In addition, not all hard particles can be held by electrodeposited metal; and, electrodepositing is limited in its range of metallic compositions as not all metals are capable of electrodeposition. Electrodepositing is not feasible with non-metallic compositions. Further, electrodepositing presents some environmental problems related to disposing of the used electrolytes.
Another prior art technique is disclosed in French application No. 69.01577, filed Jan. 24, 1969, and published under No. 2,029,390. In this application, abrasive particles are deposited into the openings in mesh material of wire, plastic or the like. While the abrasive particles reside in the openings in the mesh, metal is electroplated to secure the particles within the mesh. In one embodiment, the particles are forced into the openings in the mesh, and the mesh holds the particles until metal is electroplated thereon to secure the particles. To use this invention, therefore, one must select the size of the abrasive particles carefully; then, the electroplating does not provide sufficient strength for the resulting material to be very durable. This method is difficult to implement on a mass-production scale because the particles are not secured within the openings until metal is electrodeposited on the material, so the material would be difficult to transport before the metal is deposited.
One successful technique for providing patterns in the abrasive material is disclosed in U. S. Pat. No. 4,925,457, issued May 15, 1990, No. 5,049,165, issued Sep. 17, 1991, and No. 5,092,910, issued Mar. 3, 1992. This technique provides single and multiple layer sintered abrasive material that can subsequently be cut to shape and fixed to a substrate. Use of sinterable material, preferably processed with pressure during sintering, allows one to provide the abrasive tool with a desired combination of strength, flexibility, toughness, wear resistance, and good adherence to metallic mesh and to a variety of abrasive particles such as diamonds and cubic boron nitrides, for structural integrity. Because of this, very demanding applications can be satisfied, such as saw segments for cutting concrete, ceramic and stone, for stock removal members of grinding tools, and drill bit segments for the same materials. These materials and tools are used for such heavy duty applications as dry cutting. Electrodeposited metal does not have these advantages. If desired, of course, a plurality of specific shapes can be spaced apart on a substrate to achieve a patterned abrasive. The resulting patterned abrasive is a good quality abrasive, but the additional steps of preparing the abrasive, transporting the prepared abrasives within a manufacturing facility or between manufacturing facilities, and subsequently assembling the patterned abrasive renders the technique uneconomical for mass production of the abrasive material, and for some applications.